The present invention has a particularly advantageous, although in no way limiting, use in the case of apparatuses of the smartwatch type, in which the strap is a bracelet serving as a fastener to the wrist for them. Such smartwatches can communicate via radioelectric links in the frequency bands lower than 3 GHz, or even more, either for telecommunications functions (2G, 3G, 4G and others), for exchanges of data via Bluetooth, for communications between machines (Internet of things) such as the networks Sigfox or “Wi-Fi”, or for functions of positioning via satellites like the systems “GPS” or “GALILEO”, for example.
Another example of use of the invention is that of apparatuses of the animal collar type, allowing to locate them via positioning by satellites, or by triangulation with respect to base stations of a terrestrial access network. The apparatus communicates their position via an ultra-narrow-band wireless communication system (“Ultra Narrow Band” or UNB in the Anglo-Saxon literature), in which the instantaneous frequency spectrum of the radioelectric signals transmitted between the terminals and the access network has a frequency width of less than 1 or 2 kHz. Such ultra-narrow-band communications are subject to standards, for example the “Low Throughput Networks (LTN)” standards and draft standards of the European Telecommunications Standards Institute (ETSI).
The apparatus comprises a case containing the electronic circuit. For the radioelectric emissions and receptions, it is known to incorporate an antenna into a bracelet with a galvanic connection between the antenna and the electronic circuit.
The U.S. Pat. Nos. 4,754,285, 4,922,260, 4,977,614, 5,134,724, 5,179,733, 5,189,431, EP 1489471, U.S. Pat. No. 6,350,055 describe examples of radioelectric-telecommunication apparatuses of this type. However, it is difficult to ensure the reliability of the galvanic connection between the antenna and the electronic circuit. On the one hand, the length of the bracelet is adjustable, or even elastic, in order to adjust to various sizes of wrists. On the other hand, the bracelet is mobile with respect to the case and the galvanic connection between the antenna and the electronic circuit is physically stressed. The case of a collar for an animal has analogous difficulties.
A simple antenna structure that is more reliable is desirable.